I just moved into a new house two months ago. The house is 7 years old. I noticed some ceiling spots about a week after moving in that weren't noticed at inspection or any of the walk-throughs, but I feel sure they are old stains. They do not look like traditional water stains. They are about 1-2" in diameter and the color is consistent throughout (no halo). They are very light, which is why I don't think they were noticed until the room was completely empty. I would describe them as a light gray color. The room that they are in is a small room of the back of the house. Although the house is a two-story, this area is not under the second story. I have no attic access to this area. In the time that I have lived in the house, we have had day after day of heavy rainstorms and there have been no new spots and no change to the existing spots. This makes me believe it is not a roof leak.
They are located mainly in the center of the room. There are four of them. There is also a ventless gas fireplace in the room and a ceiling fan. I feel it worth noting that the ceiling fan was disgustingly dirty when I moved in. I have not seen so much dust before, and three of the stains are right around the fan. The other stain is above the fireplace. The old owners were also very worried about humidity in the house and actually had a humidifier installed on the furnace to make the air more humid. They thought this was good for their grand piano. When we moved in the humidifier was set at 70%. We immediately turned it down.
I did have the spots looked at by a mold expert (call me paranoid), but they aren't mold. I am thinking that maybe they are condensation stains because of the high level of humidity in the house and the ventless logs, which I also understand produce humidity. Perhaps because of all the dust in the room (as evident by the dirty fan), these spots were slightly damp and the dust stuck to them? What do you think?
I don't have pictures and painted over the spots about two weeks ago. I should add that before I painted over them I tried to clean them and a Magic Eraser made a huge difference and even made some of them disappear. So far they have not reappeared.
Sorry this is such a long post, I am just trying to provide all the information. I would love your thoughts/feedback.